I'm new to the forum so please bear with me. I own a 2008 GT/CS equipped with a Steeda CAI, hi-flo cats, Magnaflow X pipe and MBRP axle-backs. I've also installed Ford Racing 3.73 gears. The engine is tuned for 91 octane, Steeda CAI and the 3.73 rear. I started hearing a "busted muffler sound" emitting from the exhaust system. The shop I deal with inspected the exhaust system and found no problem. All clamps and clips seemed to be tight and no leaks were detected. While all of this was happening I had a check engine warning light come on. I checked to see what the check engine was all about using my Diablosport Predator tuner and the message told me I was running lean. Now here comes the weird question...Could the sound I'm hearing from my exhaust be caused by the "running lean" problem or is my shop missing something and the running lean is caused by a leaky exhaust system?